1. Field of the Invention
Some vehicles provided with independently sprung driving wheels include hub carriers through which the driving wheel supporting hub shafts are journalled. These hub shafts usually are journalled by inner and outer bearings supported in cavities within the associated hub carriers and disposed about the corresponding hub shafts. The hub carriers include bores opening thereinto by which lubrication grease may be added for greasing the bearings supported therein and the outer ends of the bores are closed by removable plugs.
However, inasmuch as the aforementioned bearings have grease seals equipped therewith which cannot withstand high pressures, a conventional high pressure grease gun may not be used for the purpose of admitting lubrication grease into the interior of the hub carrier through the aforementioned bore since excess grease pressures will "blow" the seals operatively associated with the bearings.
Accordingly, lubrication grease must be added to the interiors of the hub carriers by using special low pressure grease pumping means. This not only requires special low pressure grease pumping means but also consumes unnecessary time. Therefore, a need exists for means by which low grease pressure chambers such as those above described may have grease added thereto through an access bore by conventional high pressure grease guns in a manner preventing excess grease pressures from building up within the chambers.
2. Description of Related Art
Various different forms of lubricating fittings for use in special lubricating systems heretofore have been provided such as those disclosed in U.S. Pat. Nos. 2,234,238, 2,264,072, 2,515,611, 2,611,450 and 3,375,901. The lubricant fitting disclosed in U.S. Pat. No. 2,611,450 is of a type including means for relieving excess lubricant pressures and is functional to some degree in the desired manner. However, this pressure relieving lubricant fitting includes an external coiled band-type of pressure relief means subject to malfunction by an accumulation of dirt thereon or ice thereover.
Accordingly, a need exists for a substantially fail-safe means of lubricating a low pressure lubricant cavity through an access bore leading thereinto and in a manner which will prevent excess lubricant pressures from building up within the cavity, even though a high pressure lubricant gun is utilized to deliver lubricant to the cavity.